Justin Choi
@justinochoi.bsky.social
Baseball research! Bylines: FanGraphs, Baseball Prospectus. Former Nationals R&D.
Reposted by Justin Choi
The code is all here! The raw data is masked, as that is proprietary @baseballprospectus.com data. But BP subscribers should be able to access the same data via the leaderboards to recreate a Fully Operational simulation:
github.com/bwoodrum3/ws...
github.com/bwoodrum3/ws...
November 2, 2025 at 7:43 PM
The code is all here! The raw data is masked, as that is proprietary @baseballprospectus.com data. But BP subscribers should be able to access the same data via the leaderboards to recreate a Fully Operational simulation:
github.com/bwoodrum3/ws...
github.com/bwoodrum3/ws...
Bat speed aging curve, but this time I account for the fact that we are less likely to observe very young/old players. The corrected curve declines less rapidly early and more rapidly later compared to the regular curve, which seems like the correct inference:
November 1, 2025 at 8:05 PM
Bat speed aging curve, but this time I account for the fact that we are less likely to observe very young/old players. The corrected curve declines less rapidly early and more rapidly later compared to the regular curve, which seems like the correct inference:
Reposted by Justin Choi
Game 6 ends on a game-winning double play. The Dodgers managed to escape the ninth inning and force a Game 7.
Incredible stuff.
Incredible stuff.
November 1, 2025 at 3:15 AM
Game 6 ends on a game-winning double play. The Dodgers managed to escape the ninth inning and force a Game 7.
Incredible stuff.
Incredible stuff.
Reposted by Justin Choi
Is AWS being down an omen about the fate of the Mariners
October 20, 2025 at 3:04 PM
Is AWS being down an omen about the fate of the Mariners
Alright third of the way there, keep it up boys
Yeah just gonna need Yamamoto, Ohtani, and Glasnow to throw CGSOs. Thanks
October 15, 2025 at 3:02 AM
Alright third of the way there, keep it up boys
Reposted by Justin Choi
Gotta give props to last year’s #SMTDataChallenge winners, who created the Snell Tool (snelltool.com), which tells when to pull the starting pitcher. Tried it with Snell just now, and it said to pull him after the 8th. Looks like Dave Roberts agrees!
October 14, 2025 at 3:01 AM
Gotta give props to last year’s #SMTDataChallenge winners, who created the Snell Tool (snelltool.com), which tells when to pull the starting pitcher. Tried it with Snell just now, and it said to pull him after the 8th. Looks like Dave Roberts agrees!
Yeah just gonna need Yamamoto, Ohtani, and Glasnow to throw CGSOs. Thanks
October 14, 2025 at 3:06 AM
Yeah just gonna need Yamamoto, Ohtani, and Glasnow to throw CGSOs. Thanks
Reposted by Justin Choi
September 25, 2025 at 9:50 PM
Reposted by Justin Choi
The 2026 Big Data Bowl #BigDataBowl is live!
Participants can sign up for two competitions:
- leaderboard
- traditional analytics competition
This year's task: predict/understand player movement when the ball is in the air
Participants can sign up for two competitions:
- leaderboard
- traditional analytics competition
This year's task: predict/understand player movement when the ball is in the air
September 25, 2025 at 4:01 PM
The 2026 Big Data Bowl #BigDataBowl is live!
Participants can sign up for two competitions:
- leaderboard
- traditional analytics competition
This year's task: predict/understand player movement when the ball is in the air
Participants can sign up for two competitions:
- leaderboard
- traditional analytics competition
This year's task: predict/understand player movement when the ball is in the air
Reposted by Justin Choi
60 home runs for Cal Raleigh. Incredible.
September 25, 2025 at 3:53 AM
60 home runs for Cal Raleigh. Incredible.
Reposted by Justin Choi
Why did Luis García Jr. get fooled so badly on this pitch?
In my article representation of my SaberSeminar presentation, I answer just that and explain how visual uncertainty influences pitch tracking and helps to explain swings.
Link below.
www.mlb.com/video/luis-g...
In my article representation of my SaberSeminar presentation, I answer just that and explain how visual uncertainty influences pitch tracking and helps to explain swings.
Link below.
www.mlb.com/video/luis-g...
Luis García Jr. strikes out swinging. | 08/08/2024
Luis García Jr. strikes out swinging.
www.mlb.com
September 22, 2025 at 4:02 PM
Why did Luis García Jr. get fooled so badly on this pitch?
In my article representation of my SaberSeminar presentation, I answer just that and explain how visual uncertainty influences pitch tracking and helps to explain swings.
Link below.
www.mlb.com/video/luis-g...
In my article representation of my SaberSeminar presentation, I answer just that and explain how visual uncertainty influences pitch tracking and helps to explain swings.
Link below.
www.mlb.com/video/luis-g...
Working on a "generalized" version of dynamic dead zone (DDZ) that doesn't require any assumptions about the variables' distributions. You only need to specify the covariance structure, which is Gaussian for the sake of convenience:
September 16, 2025 at 7:41 PM
Working on a "generalized" version of dynamic dead zone (DDZ) that doesn't require any assumptions about the variables' distributions. You only need to specify the covariance structure, which is Gaussian for the sake of convenience:
Reposted by Justin Choi
Every so often we check in on the models
September 16, 2025 at 2:17 PM
Every so often we check in on the models
Reposted by Justin Choi
Induced vertical break, spin efficiency, seam-shifted wake—what do these buzzwords mean for a pitch trajectory? Explore using my Statcast-based pitch visualizer (physics modeling based on work of @pobguy.bsky.social). Updated daily with new pitching data!
gabes135.github.io/pitch-graphic/
gabes135.github.io/pitch-graphic/
Pitch Visualizer
Computational Physics Ph.D.
gabes135.github.io
September 6, 2025 at 3:27 PM
Induced vertical break, spin efficiency, seam-shifted wake—what do these buzzwords mean for a pitch trajectory? Explore using my Statcast-based pitch visualizer (physics modeling based on work of @pobguy.bsky.social). Updated daily with new pitching data!
gabes135.github.io/pitch-graphic/
gabes135.github.io/pitch-graphic/
Reposted by Justin Choi
Cal Ripken Jr has missed 3,765 consecutive games
September 6, 2025 at 11:13 PM
Cal Ripken Jr has missed 3,765 consecutive games
Alright, I've tidied up the repo and added my presentation. Thank you to everyone who was at @saberseminar.bsky.social yesterday! Was a pleasure to meet so many bright and interesting people.
github.com/justinochoi/...
github.com/justinochoi/...
GitHub - justinochoi/SaberSeminar2025
Contribute to justinochoi/SaberSeminar2025 development by creating an account on GitHub.
github.com
August 24, 2025 at 4:16 PM
Alright, I've tidied up the repo and added my presentation. Thank you to everyone who was at @saberseminar.bsky.social yesterday! Was a pleasure to meet so many bright and interesting people.
github.com/justinochoi/...
github.com/justinochoi/...
You don't truly appreciate how fast Korea's wifi is until you're standing in an endless line for border control at O'Hare
August 22, 2025 at 4:06 PM
You don't truly appreciate how fast Korea's wifi is until you're standing in an endless line for border control at O'Hare
Reposted by Justin Choi
I really enjoyed chatting with Hannah about the ups and downs of working in baseball -- and my decision to not do that anymore.
In bandwagon today, I talk to @kirio.bsky.social about working in a front office… and walking away. Including the frustrating system that makes it really hard to change jobs while staying in baseball if you find your current role isn’t the right fit. open.substack.com/pub/bandwago...
August 20, 2025 at 1:59 PM
I really enjoyed chatting with Hannah about the ups and downs of working in baseball -- and my decision to not do that anymore.
Reposted by Justin Choi
Welp, here’s the dumbest #BoothViews I’ve ever done. Here’s how it played out as my voice gave out ending today’s broadcast 🫠😂 glad Bulldog got a kick out of it!
August 18, 2025 at 3:20 AM
Welp, here’s the dumbest #BoothViews I’ve ever done. Here’s how it played out as my voice gave out ending today’s broadcast 🫠😂 glad Bulldog got a kick out of it!
Reposted by Justin Choi
America needs one of those language authorities like the French have so every person who spells it “woah” is immediately arrested.
August 17, 2025 at 2:41 AM
America needs one of those language authorities like the French have so every person who spells it “woah” is immediately arrested.
Reposted by Justin Choi
During grad school, I sent actual letters through the actual mail to five GMs, asking how a 25-year-old with an MFA in poetry and no other credentials could get involved in baseball. Only one responded, and the answer was some (polite) version of, "I regret to inform you that your dream is doomed."
FanGraphs Turns 20 Years Old Today! blogs.fangraphs.com/fangraphs-tu...
FanGraphs Turns 20 Years Old Today!
Where does the time go?
blogs.fangraphs.com
August 15, 2025 at 9:55 PM
During grad school, I sent actual letters through the actual mail to five GMs, asking how a 25-year-old with an MFA in poetry and no other credentials could get involved in baseball. Only one responded, and the answer was some (polite) version of, "I regret to inform you that your dream is doomed."
Slightly diminish a band
The Lice
The Lice
Slightly diminish a band
The Battles
The Battles
Slightly diminish a band:
2 Limited
2 Limited
August 13, 2025 at 10:28 PM
Slightly diminish a band
The Lice
The Lice
Reposted by Justin Choi
Watching baseball @jonbois.bsky.social
August 13, 2025 at 12:36 AM
Watching baseball @jonbois.bsky.social
Coming soon to a saberseminar near you: hydrogen bomb vs. coughing baby
August 10, 2025 at 9:52 PM
Coming soon to a saberseminar near you: hydrogen bomb vs. coughing baby